This invention relates in general to a high speed document transport apparatus and, in particular, to an improved augered document feeder apparatus for use with document singulation machines.
Several types of mail sorting machines exist which attempt to efficiently sort the large volumes of mail that are sent and received each day by various businesses, institutions, governmental units and other entities which handle large amounts of mail. Two major problems associated with high speed document sorting machines are assuring that the documents are properly separated from one another prior to sorting for individual handling subsequent to sorting and assuring that the documents are stable and not jostling when being fed into the singulation system which feeds the documents into the document sorting machine. If two or more documents stick together and are advanced together through the machine rather than individually, they are deposited incorrectly in the same sorting bin. Additionally, if the documents are not oriented properly to be picked off at the singulation station, the documents can be damaged.
One type of high speed document transport apparatus that has been successful is shown by U.S. Pat. No. 4,432,540 of Akers, which is commonly assigned to the present assignee. This type of machine includes a screw or auger conveyor which is placed within the magazine section of the machine and includes a pick off envelope feed station at the end of the auger conveyor for separating the individual envelopes in a stack from one another. The screw conveyor of Akers includes four driven rollers having spiral grooves for receiving the lower edges of the envelopes to convey them along the rollers as the rollers rotate. A pair of raised rollers with spiral grooves contacts a vertical edge of each envelope and maintains the envelopes in a vertical orientation as they are conveyed along the lower rollers. The pick off feed station includes a conveyor belt and a relatively strong vacuum box which draws the leading envelope against the belt. The belt then advances each envelope singly from the stack. An opposing vacuum box of lesser intensity draws any stuck envelopes away from the leading envelope to assure separation. The opposing vacuum box has a beveled surface which effects a staggered shingle arrangement of any extra envelopes adhering to the leading envelope.
Although this type of machine has been favorably received, it has not been 100% efficient. One of the problems is that the documents do not always rest stable in the horizontal and vertical directions. In order for the vacuum belts to properly separate the individual documents from the document supply, the feeding system must be able to accommodate different styles, sizes and thicknesses of documents. For example, if relatively thin envelopes are being sorted, there is a tendency for the envelopes to bunch tightly together and thus adhere to one another at the pickoff station. This tightly bunched condition of the envelopes often results in double feeding and other mispicking problems. Conversely, if the envelopes are not held together tightly enough, as tends to occur when thick documents are being handled, similar picking problems arise and the production capability of the machine also suffers.
The present invention is directed to a document feeder apparatus with an improved screw or auger conveyor to assure that the documents are transported to the document sorting machine at the proper rate and with proper orientation. In accordance with the present invention, the magazine section of the document feeder apparatus is equipped with three horizontal augers and an additional counter-rotating auger raised above the magazine section for conveying the documents to the feed station. The horizontal augers, as well as the raised auger, have two different groove pitches along their lengthwise dimensions; the pitch increases about halfway of the travel path of the documents to reduce the bunching of the documents lodged atop the auger grooves. The change in pitch of the augers provides additional separation and assures that the documents are not bunched together as they are advanced toward the feed station.
Two of the inner horizontal augers have external protrusions disposed at the root of adjacent threaded portions, the protrusions located about 180 degrees apart to jog the documents and aid in the separation process. In addition, the grooves of the raised auger are tapered in the opposite direction of the tapers of the horizontal augers and the raised auger rotates counterclockwise whereas the horizontal augers rotate clockwise as viewed from the rearward end of the magazine section. This provides a combined forward and downward force on the documents to provide proper alignment of the documents as they are transported to the document feed and sorting apparatus at the end of the feed tray. The invention includes a pickoff device comprising a belt that frictionally pulls the individual documents into the document sorting machine. The overall result is that the individual documents are effectively separated from the document supply and do not stick together as they are advanced through the machine and eventually deposited in a sorting bin.